1. Field of the Invention
The present invention relates to an image recording apparatus.
2. Description of Related Art
A known printer includes a face-up sheet discharge tray provided on a side wall of a housing and a face-down sheet discharge tray provided on an upper wall of the housing. In such a printer, for example, an upstream conveyance passage and two downstream conveyance passages may be formed. The upstream conveyance passage passes an image formation position where image formation on a recording medium is performed by an image formation unit. The two downstream conveyance passages are connected to an end of the upstream conveyance passage and guide recording sheets to the two sheet discharge trays, respectively. The conveyance destination of a recording sheet conveyed on the upstream conveyance passage is switchable by a flapper between the two downstream conveyance passages. On each of these three conveyance passages, a conveyor roller (sheet discharge roller) is provided to convey recording sheets.
In the printer above, while the downstream conveyance passage for guiding a recording sheet to the face-down sheet discharge tray may be a curved conveyance passage having a curved part which is curved, the downstream conveyance passage for guiding a recording sheet to the face-up sheet discharge tray may be a linear conveyance passage which is substantially linear in shape. In this printer, a recording sheet with at least a predetermined degree of flexibility is discharged to the face-down sheet discharge tray via the curved conveyance passage. In the meanwhile, a recording sheet without at least the predetermined degree of flexibility is discharged to the face-up sheet discharge tray via the linear conveyance passage.
In regard to the above, in the printer above, when the leading end of a recording sheet is arranged to reach the conveyor roller on the downstream conveyance passage while an image is being recorded on that recording sheet, the conveyance force of the conveyor roller is applied to the recording sheet on which the image is being recorded. In this case, if the conveyance speed of the conveyor roller on the downstream conveyance passage is arranged to be equal to or higher than the conveyance speed of the conveyor roller on the upstream conveyance passage, the recording sheet is pulled downstream after the leading end of the recording sheet reaches the conveyor roller provided on the downstream conveyance passage. As a result, the recording position of the image on the recording sheet recorded by the image formation unit is deviated, and hence the quality of the image recorded on the recording sheet is deteriorated.
For this reason, in the printer above, the conveyance speed of the conveyor roller provided on the curved conveyance passage on which a flexible recording sheet is conveyed is arranged to be lower than the conveyance speed of the conveyor roller provided on the upstream conveyance passage. As the conveyance speeds are arranged in this way, when an image is recorded on a flexible recording sheet, the recording sheet is warped between the conveyor roller on the upstream conveyance passage and the conveyor roller on the curved conveyance passage, with the result that the recording sheet is not pulled downstream and hence the deterioration in the quality of the image recorded on the recording sheet is restrained. In this regard, the conveyance speed of the conveyor roller provided on the linear conveyance passage on which a recording sheet without at least the predetermined degree of flexibility is conveyed is arranged to be substantially identical with the conveyance speed of the upstream conveyor roller, because, for example, the recording sheet cannot be warped.
An image recording apparatus is preferably able to record an image on a recording sheet which is longer than a regular recording sheet. In the printer above, provided that the conveyance speed of the conveyor roller provided on each conveyance passage is arranged as described above, when a long recording sheet is discharged to the face-down sheet discharge tray via the curved conveyance passage, the amount of warpage of the recording sheet between the conveyor rollers is larger than the amount of warpage of a regular recording sheet. The inventor of the subject application has found that, when an image is formed at around the tail end of such a recording sheet by the image formation unit, the quality of the image recorded on the recording sheet is deteriorated on account of a large amount of warpage of the recording sheet.
In the meanwhile, when a long recording sheet is discharged to the face-up sheet discharge tray provided on the side wall of the housing, the deterioration in the quality of the image recorded on the recording sheet is restrained as compared to the case where the recording sheet is discharged to the face-down sheet discharge tray. However, a large space to which a long recording sheet is discharged must be provided at a side of the housing, with the result that the installation space of the image recording apparatus is large.